Fast Transient Overvoltage Analysis in Current Transformers due to Disconnector Switching Operation

This paper presents the results of a computer simulation analysis combining the application of energy spectral density techniques and evaluation of the rate of rise for checking the voltage withstand of the dielectric system of a current transformer under the incidence of a set of fast transient voltage surges caused by switching operations of an adjacent disconnector. This sort of occurrence has become a critical issue in the electrical power system, being a possible cause of the high number of failures of operating current transformers 550 kV class. The adopted approach is rather new and differs from any of those applied to the analyses of the incidence of VFTO – Very Fast Transient Overvoltage by representing a contribution to the discussions for updating current transformer testing standards.